Negan is not a loophole of racism, sure you can say it sounds similar but it is a name and there wasn’t even any offensive context like (TOU spoiler, be aware)
as an example to loophole the rule.
You’ve done nothing wrong by the looks of it and I hope this will get solved for you, the staff members in question will just need to understand situations like these much better next time. No excuses to say the nword either, I don’t care who it is but they’re clearly being arseholes.